host: Don't leak file descriptors from attach
host: Don't leak file descriptors from attach

The fds passed from containerinit need to be closed once we're
finished with them.

Signed-off-by: Jonathan Rudenberg <3692bfa45759a67d83aedf0045f6cb635a966abf@titanous.com>

lmars/flynn,flynn/flynn,flynn/flynn,philiplb/flynn,philiplb/flynn,flynn/flynn,philiplb/flynn,lmars/flynn,flynn/flynn,lmars/flynn,lmars/flynn,philiplb/flynn,lmars/flynn,flynn/flynn,philiplb/flynn